The present invention generally relates to liquid drainage apparatus, and more particularly to vacuum drainage systems for waste water.
Health and Environmental agencies require waste water to be collected and directed to a proper receptacle, such as a municipal sewer or private septic tank. The term xe2x80x9cwaste waterxe2x80x9d includes used or dirty process water (known as gray water), and sewage water (commonly referred to as black water). Gray water may be generated from a variety of different operations. In a grocery store, for example, water is used in deli, food service, and floral departments for cleaning, maintenance, and other purposes. Refrigerated display cases generate additional process water from condensate and defrost procedures. The waste water generated from these various sources must be collected and transported to the proper receptacle.
In the past, conventional gravity drainage piping has been used to collect and transport waste water. Gravity drainage systems use collection points located below the waste water source which feed into drainage pipes leading to a sewer line. The piping in such systems must be continuously sloped so that the waste water flows all the way to the sewer line. As a result, pipes for gravity drainage systems are often laid in or underneath the concrete pad supporting the facility. This process not only requires significant amounts of additional plumbing work, but also complicates changes in facility layout, which require portions of the concrete pad to be ripped up to expose drainage channels.
More recently, vacuum drainage systems have been used to collect and transport waste water. A vacuum drainage system typically comprises a collection drain located under each waste water source, each collection drain leading to a common drain pipe. The drain pipe is connected to a pump which creates negative pressure in the drain pipe to thereby pull liquid through the drain pipe and into the collection tank. The tank has a drain that is typically positioned over a sewer line to allow the tank to be emptied.
Significantly, vacuum drainage systems allow the use of overhead drainage piping since suction rather than gravity is used to transport the waste water. Vacuum drainage piping does not need to be laid in concrete below the waste water source, but instead may follow overhead electrical and refrigeration service lines. Thus, plumbing layouts are simplified and water generating equipment may be quickly and easily relocated within a facility without ripping up concrete. As a result, greater freedom exists for redesigning the facility layout.
While the use of overhead piping provides certain advantages, the pumps used in vacuum drainage systems are capable of lifting only a limited volume of water from the collection drains to the vacuum drainage piping. Certain systems provide a buffer section consisting of a large diameter pipe into which waste water initially collects. An air intake is provided to allow air at atmospheric pressure to access liquid in the pipe. Once the desired volume of water has collected in the buffer, a valve leading to the vacuum drainage piping is opened so that waste water travels toward the valve. Air entering the intake opening creates a pressure differential across the waste water which acts to lift the waste water toward the vacuum drainage piping. Once the waste water reaches the vacuum drainage piping, the valve shuts so that additional water may collect in the buffer and the process is repeated. In this manner, conventional vacuum drainage systems lift discrete volumes or xe2x80x9cslugsxe2x80x9d of waste water to the vacuum drainage piping.
It is difficult, however, for such conventional systems to ensure that an appropriate volume of waste water is pulled toward the vacuum drainage piping. Care must be taken so that the slug of waste water is not too large for the pump. Conversely, slugs that are too small cause unduly rapid cycling of the valve. As a result, it is overly difficult to efficiently transport unbroken slugs of liquid using conventional vacuum drainage systems.
In accordance with certain aspects of the present invention, a vacuum drainage system is provided for evacuating waste water, the system including a pump having an inlet, a collection tank in fluid communication with the pump inlet, a drainage pipe fluidly communicating with the tank, and a valve connected to the drainage pipe. The system also includes a buffer box defining a reservoir and having an outlet in fluid communication with the valve, an inlet allowing fluid flow into the reservoir, and an air intake orifice. The system further includes an activator coupled to the valve and having a sensor which detects fluid level in the reservoir, the activator opening the valve when the sensor detects a particular fluid level height.
The reservoir may be sized to have a known effective volume. In addition, the air intake orifice of the buffer box may be located within an upstream ⅓ of the buffer box, and may have a cross-sectional area at least equal to a cross-sectional area of the inlet. The air intake orifice and outlet may be sized so that a ratio between air intake orifice size to outlet size is approximately 1.7:1. Fluid inlet size to outlet size is preferably 2:1 to 3.5:1. The buffer box may further comprise a pressure chamber depending from a cover portion of the buffer box into the reservoir and fluidly communicating with a sensor port, and the sensor may be a pressure sensor. The outlet of the buffer box may have a fence portion which reduces the height of an upper edge of the outlet.
In accordance with additional aspects of the present invention, a buffer box is provided for use in a liquid evacuation system. The evacuation system includes a pump and a collection tank in fluid communication with an inlet of the pump. A drainage pipe fluidly communicates with the tank and a valve is attached to the drainage pipe. An activator is coupled to the valve and has a liquid level sensor. The buffer box includes a body defining a reservoir for holding a known effective volume of liquid. The body has an inlet which allows liquid to flow into the reservoir, an outlet adapted for fluid communication with the valve, an air intake orifice open to atmosphere, and a sensor port adapted for use with the liquid level sensor. The activator opens the valve when the sensor detects a particular liquid level height in the reservoir.
In accordance with further aspects of the present invention, a method of evacuating liquid from a reservoir up a vertical pipe is provided. The pipe has an upper end in communication with a pump which creates negative pressure in the pipe, a lower end in fluid communication with the reservoir, and a valve located between the pump and the reservoir. The method comprises an initial step of collecting liquid in a buffer box having a known effective volume, the buffer box having an air intake orifice. The valve is then opened to create a pressure differential across the liquid in the buffer box, the pressure differential being formed by the negative pressure in the vertical pipe acting on an upstream end of the liquid and atmospheric air entering through the air intake orifice to act on an upper surface of the liquid collected in the buffer box. The valve is then closed after the liquid passes through the vertical pipe. As a result, substantially consistently sized slugs of water are pulled up the vertical pipe.
Other features and advantages are inherent in the apparatus claimed and disclosed or will become apparent to those skilled in the art from the following detailed description and its accompanying drawings.